Analytical solution of diffusion equations in multicomponent systems when applying diffusion coatings

For multicomponent coatings, analytical equations are obtained that take into account the diffusion coefficients in the concentration equations. It is shown, that to solve the problem of multicomponent diffusion in a solid solution containing substitutional elements and interstitial elements, it is advisable to use the equations for the concentrations of chemical elements. Keywords: multicomponent coating, solid solution, concentration, diffusion coefficient, analytical solution [email protected]

Diffusimetry Renounces Graham’s Law, Achieves Diffusive Convection, Concentration Gradient Induced Diffusion, Heat and Mass Transfer

Absolute diffusion rates of KMnO4 in vertical and flattened diffusimeters show the concentration gradient force as being stronger than the gravitational force. Hot water molecules move downward on self-diffusion against buoyancy. Diffusive convection (DC) in warm water and double-diffusive convection (DDC) in warm, saline water take place inside the diffusimeter with DDC transferring more heat than DC. In the diffusing medium the original reagents change or retain their compositions to give the diffusate molecules to diffuse. In water, the change is mostly hydration. The syngener BaCl2.2H2O separately with congeners 3CdSO4.8H2O, ZnSO4.7H2O, and ZnSO4.H2O presents two distinct pairs of overlapping concentration versus rate curves, first for having very close MWs of BaCl2 and CdSO4 and second for having ZnSO4.H2O as the common congener for both the zinc sulfates. Chlorides of Li, Na, and K diffusing at hindered rates in glucose solution show the least rate for LiCl inevitably on grounds of low mass and high Li+ hydration radius. Diffusion blocking occurs at higher glucose concentration. Diffusion of 0.6M AgNO3-0.6M NH4Cl standardizes this diffusimeter. Mass transfer of HCl, H2SO4, and H2C2O4 show oxalic acid diffusing as hydrate and 88 percentage transfer of sulfuric acid in 5 minutes. The Superdiffusive Anti Graham’s Law, Vd , is further consolidated by Ca (NO3)2-M2CO3(M = Na, K, NH4+) and Ca (NO3)2-Na2HPO4 diffusions. Odd and even diffusions are illustrated by AgNO3-NH4Cl and AgNO3-BaCl2 diffusions.

AC Electroosmosis Effect on Microfluidic Heterogeneous Immunoassay Efficiency

A heterogeneous immunoassay is an efficient biomedical test. It aims to detect the presence of an analyte or to measure its concentration. It has many applications, such as manipulating particles and separating cancer cells from blood. The enhanced performance of immunosensors comes down to capturing more antigens with greater efficiency by antibodies in a short time. In this work, we report an efficient investigation of the effects of alternating current (AC) electrokinetic forces such as AC electroosmosis (ACEO), which arise when the fluid absorbs energy from an applied electric field, on the kinetics of the antigen–antibody binding in a flow system. The force can produce swirling structures in the fluid and, thus, improve the transport of the analyte toward the reaction surface of the immunosensor device. A numerical simulation is adequate for this purpose and may provide valuable information. The convection–diffusion phenomenon is coupled with the first-order Langmuir model. The governing equations are solved using the finite element method (FEM). The impact of AC electroosmosis on the binding reaction kinetics, the fluid flow stream modification, the analyte concentration diffusion, and the detection time of the biosensor under AC electroosmosis are analyzed.

Modeling the Kinetics of Saline Minerals Dissolution in Dombrovsky Quarry at the Kalush-Golinsky Potassium Salts Deposit

The article deals with the peculiarities of the chemical composition formation of brines in the Dombrovsky quarry, primarily due to the dissolution of potash ore minerals and host rocks in water coming from the pebble horizon and atmospheric precipitation. The solubility of the ore body minerals has been studied, and it ranges from 333 to 502 g∙dm–3. The boundary conditions for the formation of a saturated salt solution were determined. The estimated concentration of saturated potash ore solution under normal conditions is 426 g∙dm–3. The mechanism of dissolution is considered from the standpoint of D.I. Mendeleev's chemical theory of solutions. The temporary dynamics of minerals dissolution of the ore body is studied experimentally. The parameters of kinetic-diffusion process are calculated. The rate of the dissolution process, which occurs in the kinetic region, significantly exceeds the rate of concentration diffusion of hydrated ions: from 5 to 400 times depending on the mineral composition of salts. Theoretically from the point of view of multistage process kinetics and experimentally in laboratory conditions it is proved that the process that determines the formation of the chemical composition of brines (the slowest stage) is the concentration diffusion of hydrated ions Na+, K+, Cl–. They enter the liquid phase due to the minerals dissolution of the ore body and host rocks of soil and sides of the quarry, in the direction of overcoming the concentration difference - from the lower layers of the brine to its surface. This conclusion is confirmed by the ratio of weight coefficients а1 and а2. The contribution of the process of the main minerals dissolution of the ore body to the chemical composition formation of the solution is significantly less than the concentration diffusion process.

Modeling the Optimal Conditions for Improved Efficacy and Crosslink Depth of Photo-Initiated Polymerization

Optimal conditions for maximum efficacy of photoinitiated polymerization are theoretically presented. Analytic formulas are shown for the crosslink time, crosslink depth, and efficacy function. The roles of photoinitiator (PI) concentration, diffusion depth, and light intensity on the polymerization spatial and temporal profiles are presented for both uniform and non-uniform cases. For the type I mechanism, higher intensity may accelerate the polymer action process, but it suffers a lower steady-state efficacy. This may be overcome by a controlled re-supply of PI concentration during the light exposure. In challenging the conventional Beer–Lambert law (BLL), a generalized, time-dependent BLL (a Lin-law) is derived. This study, for the first time, presents analytic formulas for curing depth and crosslink time without the assumption of thin-film or spatial average. Various optimal conditions are developed for maximum efficacy based on a numerically-fit A-factor. Experimental data are analyzed for the role of PI concentration and light intensity on the gelation (crosslink) time and efficacy.

Modeling the Strategies for Improved Efficacy and Crosslink Depth of Photo-Initiated Polymerization and Phototherapy

Optimal conditions for maximum efficacy of photoinitiated polymerization are theoretically presented. Analytic formulas are shown for the crosslink time, crosslink depth and efficacy function. The roles of photoinitiator (PI) concentration, diffusion depth and light intensity on the polymerization spatial and temporal profiles, for both uniform and non-uniform cases, are presented. For optimal efficacy, a strategy via controlled PI concentration is proposed, where re-supply of PI in high light intensity may achieve a combined-efficacy similar to low light intensity, but has a much faster procedure. A new criterion of efficacy based on the polymerization (crosslink) [strength] and [depth] is introduced. Experimental data are analyzed for the role of PI concentration and light intensity on the gelation time and efficacy.